coates and j



F. COMES ND 1. Mmm. EARTHING DEVICE FOR ELECTRIC OIL BREAK SWITCHES.

APPLICATION FILED DEC 7. |918.

Patented Dea. 23,1919.

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F. CATES AND1. MIRREY.

EARTHING DEVICE FOR ELECTRIC OIL BREAK SWITCHES.

APPLICATION FILED mac.:I 191s.

1 ,326,028. Patented Dec. 23, 1919.

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l fr; y-flmm nali UNITED STATES PATENT OFFICE.

FRANK COATES, OF CLEADON, AND JAMES MIRREY, OF EAST BOLDON, ENGLAND, ASSIGNGRS TO A. REYROLLE & COMPANY LIMITED, 0F HEBBURN-ON-TYNE,

ENGLAND.

EARTHING DEVICE FOR ELECTRIC OIL-BREAK SWITCHES.

Application led December 7, 1918.

To all 'whom t may concern.'

Be it known that we, FRANK CoA'rEs and JAMES MIRREY, subjects of the King of England, and residing at Cleadon, Durham, England, and East Boldon, Durham, England, respectively, have invented certain new and useful vImprovements in Earthing Devices for Electric Oil-Break Switches, of which the following is a specification.

This invention relates to earthing devices for electric oil-break switches and is primarily concerned with the earthing of the conductors of an insulating switch to insure safety in handling such conductors when uncovered by the removal of the oil tank.

In good modern practice on high voltage systems it is usual to provide isolating or interlocking arrangements for the purpose of insuring that the conductors are disconnected before the oil tank is lowered `and in some cases the removal of the tank is positively prevented by some interlocking devices until such isolation has been accomplished. Such arrangements under certain conditions are insufficient owing to the possibility of leakage of current through the isolating device due say to the presencev of dirty oil. Again the conductors of the switch may be accidentally charged with a dangerous voltage through the inductive effect of a current in a neighboring conductor. Or the conductor may retain a charge due to its own electrostatic capacity. Thus there may be danger in handling the conductors of a switch although such switch may be isolated so far as the mere opening of switch members is concerned. The object of the present invention is to prevent such a contingency from arising and to make absolutely sure that the conductors are safe to handle.

An electric oil-break switch according to this invention is provided with one or more earthing members so arranged and disposed that the conductors or contacts within the oil tank must be earthed before they are rendered accessible by the removal of the tank.

In one construction the earthing member is in the forni of a pivoted arm or blade within the oil tank operated by mechanism outside the tank and connected to the pivoted arm say by a plunger passing through the cover of the tank. The operating mechanism which may be of any suitable kind Specification of Letters Patent.

Patented Dec. 23, 1919.

sei-iai No. 265,778.

is so interlocked with the gear for lowering or otherwise removing the tank that such gear cannot be operated to remove the tank until the conductors within the tank have first been earthed, through the movement of the pivoted arm.

In another construction also accordingv 'which form the contacts of the switch.

Preferably each arm is provided withy a spring contact blade carrying` a contact with rounded edges so that as the arm moves downward the contact on the spring blade makes easy but sure contact with the conductor. In such a construction arrangements are made whereby the earthing members are held inoperative when the oil tank is in its normal closed or on position. For instance each of the pivoted arms may be provided with a projecting portion or lug which when the tank is raised into its on position, is engaged by a bracket or the like fixed on the inside wall of the tank so that the arm is raised against the action of its spring. During the removal of the tank and before the switch contacts are rendered accessible by such removal, the withdrawal of the brackets or the like releases thev pivoted arms which consequently move under the action of the spring and make earthing contact with the switch conductors. The replacement of the oil tank into its on position automatically withdraws the earthing members from their connection with the switch conductors and resets them in their normal position ready to operate again in the manner described.

A similar resetting arrangement may be provided in the construction first mentioned in which the movement of the earthing member is brought about by mechanism from outside the tank.

In the accompanying drawings,

Figure 1 is a sectional elevation of an oilbreak isolating switch provided with one construction of earthing device according to this invention.

Fig. 2 is a side elevation of the mechanism for operating the earthing device.

Figs. 3 and L are respectively a plan and an elevation of a portion of another form of earthing device also according to this invention, and

Fig. 5 is a sectional elevation of the upper portion of an isolating switch having two earthing members similar in construction to that shown in Figs. 3 and 4.

All the figures are purely diagrammatic and various parts of the switch gear not essential to the present invention are omitted.

Vith reference first to Figs. l and 2 the oil tank A is shown lprovided with raising and lowering gear operated from a shaft .B having a crank handle B. The isolating switch C contained in the tank is shown conventionally as operated by a rod C and as is well known in oil-break isolating switches the mechanism for opening the switch C may be interlocked with the shaft B so that the tank A cannot be lowered until the switch C has been opened. With this interlocking mechanism however the present invention is not concerned. Two conductors D D are shown passing through the fixed cover of the tank to the switch C and one of 'these D is provided with a contactY E which maybe connected to earth c. g. to the cover of the tank when a pivoted contact arm F is moved downward by means of a rod F. Any convenient means may be provided for operating this rod F but in the construction shown in Figs. l and 2 it is moved by means of a pin engaging with the slotted crank Cr on a spindle G furnished with a handle G2.

To insure that the earthing switch F must be moved into connection with the contact E thus earthing the conductor D, before the tank A can be lowered, interlocking mechanism is provided between the earthing switch and the tank-lowering gear. In the construction illustrated this is shown by way of example as an engagement between the upper portion of the rod F and a pulley-like boss H on the shaft B. The member H has a hole or recess in its periphery into which the end of the rod F passes when it is in its raised position and thus until the rod F is .withdrawn by partially rotating the shaft G the shaft B cannot be rotated to lower the oil tank A. The movement of the shaft G necessary to withdraw the rod F from the member H causes the earthing switch F to move down and make connection with the contact` E.

The arrangement may be such that the contact between the members F and E cannot be broken that is to say the conductor D must remain earthed until the tank is conductors D2 again raised. Obviously in the example illustrated this might be brought about by proportioning suitably the diameters ofthe pulleys B2 controlling the vertical movement ofthe tank A. For if less than one revolution of the shaft B is necessary for the complete lowering of the tank then the arrangement may be such that the rod F cannot be returned into the hole or recess inthe member H until the sha ft B has been rotated back into the position shown in the drawings. y

In the construction shown in Figs. 3 and a the earthing switch instead of being operated independently before the lowering of the tank is moved automatically into position to earth the conductors during the removal of the tank and before the conductors are rendered accessible. )n this construction the earthing switch n2 is in tlie85 form of an arm pivoted at J in a bracket K attached say to the cover of the tank A. Around the spindle J is coiled a spring J one end of which vbears against a portion of the arm F2 and tends to force that arm 90 down into the position shown in chain lines in Fig. 4C. Then in that position the spring contact F3 on the earthing switch makes rubbing connection with one of the switch and earths that member. vWhen the oil tank A is in its raised position a bracket A2 fixed to the tank A engages with alug F4 forming part of the switch arm F2 and raises that member against the action of the spring J into the 100 position shown in full lines in Figs. 3 and 4c.

rFhe initial lowering movement of the tank A withdraws the bracket A2 and allows the earthing switch F2 to move down under the action of the spring J and earth the conductor D2 before the tank has been lowered sufficiently to render the conductors in the tank accessible.

The switch arm F2 is shown provided with a projection or lug F5 which forms a limit- 110 ing stop for the downward movement of the arm F2 yby engaging with the web of the bracket K. When the tank A is replaced the bracket A2 again engages with the end of the lug F2 and lifts the arm F2 up into 115 its normal position against the action of the spring J.

The construction shown in Fig. 5 is similar in form and operation to that described with reference to Figs. 3 and l eXcept that 120 two earthing switches F 6 and F7 arel provided one for each of the conductors D3 and D4. The switch arms F G and F 7 are mounted on a bracket K on the tank cover A3 and are spring operated as previously described the arms being retained in their off position when the tank is Vraised by brackets A4 and A5 one of the brackets preferably being on one side of the tank and the other on th opposite side. y l l K p u *.180

It is understood that the constructions shown are purely by way of example and that any suitable forms of earthing switches may be employed and may be interlocked with the tank lowering gear or operated by the raising and lowering of the tank in any appropriate way.

Although the invention has been described with particular reference to an isolating switch it may be applied to any electric oilbreak switch having1 one or more conductors which it is desirable to earth before the oil tank is removed.

Oil is referred to in the specification as the insulating liquid but obviously other known liquids suitable for the purpose may be employed.

What we claim as our invention and desire to secure by Letters Patent is l. The combination of an electric oilbreak switch, a tank therefor, a movable earthing member within the tank, and means for moving the earthing member into contact with a conductor within the tank, to earth such conductor before it is rendered accessible by the removal of the tank.

2. The combination of an electric oilbreak switch, a tank therefor, an earthing .member mounted so that it can be moved into contact with a conductor within the tank, mechanism outside the tank for moving the earthing member, gear for lowering or otherwise removing the tank and means for interlocking the mechanism for moving the earthing member with the lowering gear so that the tank cannot be removed until the conductor is earthed.

3. The combination of an electric oilbreak switch, a tank therefor, a movable earthing member within the tank, and means for automatically moving the earthing member into contact with a conductor within the tank to earth such 'conductor during the removal of the tank and before such conductor is rendered accessible.

4. The combination of an electric oilbreak switch, a tank therefor, and a springoperated earthing member within the tank arranged so that it is moved automatically into contact with a conductor within the tank during the removal of the tank and before such conductor is rendered accessible.

5. The combination of' an electric oilbreak switch, a tank therefor, a spring-operated earthing member within the tank arranged so that it is moved automatically into contact with a conductor within the tank during the removal of the tank and before such conductor is rendered accessible and means whereby the earthing member is restored to its normal position when the tank is replaced.

6. The combination of an electric oilbreak switch, a tank therefor, a cover to said tank, an earthing switch arm pivotally mounted on the inside of the cover, a spring tending to cause the earthing switch arm to move into contact with one of the oil-break switch conductors in the tank and a proj ecting member on one of the side walls of the tank, such projecting member engaging with the earthing switch arm and preventing its movement under the action of the spring until the tank is withdrawn.

In testimony whereof we have signed our names to this specification.

FRANK COATES. JAMES MIRREY. 

